Video Lecture
Theory For Making Notes
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Practice Questions (Basic Level)
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Practice Questions (JEE Main Level)
1.
A gas of hydrogen like atoms can absorb radiations of 68 eV. Consequently, the atoms emit radiations of only three different wavelengths. All the wavelengths are equal or smaller than that of the absorbed photon.
(a)
Determine the initial state of the gas atoms.
(a) 28.5 Å
(b) 46.3 Å
(c) 1.7 Å
(d) 3.4 Å
Ans (a)
(b)
Identify the gas atoms.
(a) n = 2, Z = 9
(b) n = 2, Z = 1
(c) n = 2, Z = 2
(d) n = 2, Z = 6
Ans (d)
(c)
Find the minimum wavelength of the emitted radiations.
(a) 25.32 Å ,
(b) 0.76 Å
(c) 2.3 Å
(d) 12.3 Å
Ans (a)
(d)
Find the ionization energy and the respective wavelength for the gas atoms.
(a) 450.2 eV
(b) 489.6 eV
(c) 328.4 eV
(d) 423.5 eV
Ans (b)
2.
A 100-W bulb converts 5% of the electrical energy input to visible light. Assume the light has a wavelength of 600 nm and the bulb is a point source.
(a)
What is the number of photons emitted per second?
(a) 1.51 x 1019s-1
(b) 0.51 x 1019s-1
(c) 4.51 x1019s-1
(d) 9.51 x1019s-1
Ans (a)
(b)
If the eye can detect 20 photons/s, at what distance would the bulb be visible? Take the pupil diameter to be 3 mm.
(a) 700 km
(b) 38 km
(c) 150 km
(d) 652 km
Ans (d)
3.
A hydrogen atom emits radiation of wavelength 102.5 nm. What are the n values of the two levels involved?
(a) n = 1, 1
(b) n = 1, 3
(c) n = 1, 2
(d) n = 1, 9
Ans (b)
4.
The electron in the hydrogen atom is in the n = 2 state. What is its
(a) potential energy
(a) – 6.8 eV
(b) – 6.2 eV
(c) – 7.4 eV
(d) -2.5 eV
Ans (a)
(b)
kinetic energy?
(a) 0.3 eV
(b) 3.4 eV
(c) 9.2 eV
(d) 11.5 eV
Ans (b)
5.
What is the maximum wavelength that can ionize a hydrogen atom in the ground state? In what region of the electromagnetic spectrum does this wavelength lie?
(a) 20.5 nm
(b) 55.3 nm
(c) 73.9 nm
(d) 91.2 nm
Ans (d)
6.
What is the shortest wavelength
(a)
in the Balmer series
(a) 2000 Å
(b) 3050 Å
(c) 3650 Å
(d) 4000 Å
Ans (c)
(b)
in the Lyman series?
(a) 914 Å
(b) 948 Å
(c) 1000 Å
(d) 2000 Å
Ans (a)
Practice Questions (JEE Advance Level)
1.
A gas of identical hydrogen like atoms has some atoms in the lowest (ground) energy level A and some atoms in a particular upper (excited) energy level B and there are no atoms in any other energy level. The atoms of the gas make transition to higher energy level by absorbing monochromatic light of photon 2.7 eV. Subsequently, the atoms emit radiation of only six different photon energies. Some of the emitted photons have energy 2.7 eV, some have energy more and some have less than 2.7 eV.
(a)
Find the principal quantum number of the initially excited level B.
(a) Z = 0
(b) Z = 1
(c) Z = 5
(d) Z = 10
Ans (b)
(b)
Find the ionization energy for the gas atoms.
(a) -13.6 eV
(b) -3.23 eV
(c) -4.36 eV
(d) -10.3 eV
Ans (a)
(c)
Find the maximum and the minimum energies of the emitted photons.
(a) 12.75 eV, 0.29 eV
(b) 12.75 eV, 0.33 eV
(c) 12.75 eV, 0.16 eV
(d) 12.75 eV, 0.66 eV
Ans (d)
2.
A m – meson which is 210 times as heavy as an electron and having charge equal to that of an electron is captured by a proton to form a hydrogen – like atom.
(a)
What is the energy of the photon that is emitted when a \displaystyle \mu – meson falls from the first excited state to the ground state ?
(a) 2122 eV
(b) 2142 eV
(c) 2022 eV
(d) 1187 eV
Ans (b)
(b)
What is the radius of the first Bohr orbit ?
(a) 0.0023 Å
(b) 0.045 Å
(c) 1.0059 Å
(d) 10.67 Å
Ans (a)
(c)
What is the velocity of the \displaystyle \mu – meson in the first circular Bohr orbit ?
(a) 0.36 x 106 m/s
(b) 1.75 x 106 m/s
(c) 2.19 x 106 m/s
(d) 5.67 x 106 m/s
Ans (c)
3.
The atom of a positronium consists of an electron and a positron orbiting about each other.
(a)
Find the Bohr radius of this system.
(a) 2.54 Å
(b) 5.38 Å
(c) 0.3 Å
(d) 1.06 Å
Ans (d)
(b)
Find the wavelength of the photon released in the transition from n = 2 to n = 1.
(a) 2235 Å
(b) 2054 Å
(c) 2431 Å
(d) 1235 Å
Ans (c)
4.
A monochromatic light source of frequency f illuminates a metallic surface and ejects photoelectrons. The photoelectrons having maximum energy are just able to ionize the hydrogen atoms in ground state. When the whole experiment is repeated with an incident radiation of frequency \frac{5}{6}f, the photoelectrons so emitted are able to excite the hydrogen atom beam which then emits a radiation of wavelength 1215Å.
(a)
Find the work function of the metal.
(a) 4.35 x 1015Hz
(b) 1.53 x 1015Hz
(c) 0.23 x 1015Hz
(d) 4.92 x 1015Hz
Ans (d)
(b)
What is the frequency of radiation .
(a) 1.3 eV
(b) 6.8 eV
(c) 9.5 eV
(d) 10.8 eV
Ans (b)
5.
A hydrogen like atom (atomic number Z) is in a higher excited state of quantum number n. This excited atom can make a transition to the first excited state by successively emitting two photons of energies 10.20 eV and 17.00 eV respectively. Alternatively, the atom from the same excited state can make a transition to the second excited state by successively emitting two photons of energies 4.25 eV and 5.95 eV respectively. Determine the values of n and Z. (ionization energy of hydrogen atom = 13.6 eV).
(a) n = 3, Z = 6
(b) n = 6, Z = 3
(c) n = – 6, Z = – 3
(d) n =-3, Z = – 6
Ans (b)